Filters for fluids, including liquids and gases, have been known in the art. For instance, filters are commonly used in such systems as air filtration systems, water filtration systems, water purification systems, and the like. A common type of filter is a cartridge-type filter with a replaceable filter typically mounted on a core and placed into a filtration system. The replaceable filter is typically formed from a porous, relatively soft material having pores sized to prevent contaminants and/or other particles (hereinafter “contaminants” for the sake of convenience and without intent to limit) from flowing through the filtration system, while letting the fluid pass therethrough. However, contaminants and particles typically become embedded in such filters such that the filters must be replaced on a regular basis.
Typically, cartridge-type filters are cylindrical elements having a substantially open longitudinal center portion with radially-outwardly extending, longitudinal folded portions or pleats. A plurality of pleats is commonly arranged around a tubular core defining a cylinder. When viewed in a transverse cross-section, the pleats typically extend radially outward from the core toward the outer periphery of the filter. A drawback of this pleated design is that, because the filter industry has become standardized, the overall dimensions of the filter body are restricted and it therefore becomes difficult to increase the size of a filter beyond the conventional dimension of the filter body. Thus the filter capacity and effectiveness are limited by the surface area of the filter cartridge.
Because the effectiveness of the standard cartridge-type filter is generally a function of the surface area of the filter, several attempts have been made to modify the pleat design in order to increase the available surface area. For example, attempts have been made to modify the length at which a pleat extends from the center core toward the periphery of the cartridge. In one example, an attempt has been made to form pleats that are radially curved rather than having pleats that extend linearly from the core of the cartridge. The increase in the length of each radially curved pleat was intended to result in an increased surface area of the filter.
Despite these several attempts, conventional filter technology has been unable to achieve significant increases in surface area while maintaining industry accepted standards for overall filter dimensions. Accordingly, it would therefore be desirable to form a filter that has an increased surface area for removing contaminants from a fluid stream. The increase in surface area could in turn provide for an increased filtering capacity, and/or an increase in the effective service life of the filter.